Trump’s decision is likely to incite unrest in the region where for more than 70 years most countries have stayed out of the dispute over who owns one of the most significant religious areas in the world.

Why are some saying the move will cause chaos in the region? Here’s a look at what the decision could mean.

What is happening Wednesday?

The president declared Jerusalem the capital of Israel and announced plans to move the US embassy from its current location in Tel Aviv to Jerusalem.

The move will not take place immediately.

In addition, Trump reasserted his commitment to supporting a two-state solution if Israel and Palestine can come to that agreement.

Why is that causing so much commotion?

Jerusalem is the center of the conflict between Israel and Palestine. Israel has called Jerusalem its undivided capital, while Palestine claims the eastern half of the city as its capital.

In 1947, the United Nations worked to create a homeland for Jews in the Middle East with the idea that Jerusalem would be a separate “international city.” However, the war to establish an Israeli state led to the city being divided.

In 1949, the “Green Line” (a border created through negotiations at the end of the war) was established, giving Israel the western half of Jerusalem and Jordan the eastern half.

That arrangement lasted for nearly 20 years until the Six-Day War in 1967 at which time Israel occupied East Jerusalem and has kept it since then.

In 1980, Israel passed a law stating Jerusalem was the united capital of Israel.

While Israel claims Jerusalem, the rest of the world has refrained from assigning capital status to either side until and unless Israel and Palestine can come to an agreement on who owns what. Resolving that issue is perhaps the most difficult part of finding a peaceful end to the Palestinian-Israeli conflict.

The United States keeps its embassy in Tel Aviv, like most other countries. Also, like other countries, the U.S. has a consulate in Jerusalem.

If the United States declares Jerusalem the capital of Israel, it will be the first country to officially do so since the country’s inception in 1948. Compounding the issue is that Jerusalem is home to key sacred sites for Jews, Christians and Muslims.

The United States has not moved the embassy to Jerusalem because for 70 years countries around the world have stayed out of the conflict over who owns the city.

In 1989, however, the U.S. began leasing a plot of land in Jerusalem that was to be the spot where a new embassy was to be built. The 99-year lease costs the United States $1 a year. The land remains undeveloped. There is a U.S. consulate in Jerusalem.

In 1995, Congress passed a law that required the embassy to be moved to Jerusalem, saying if Israel claims Jerusalem as its capital, then the U.S. should respect that.

Since that law passed, every U.S. president, citing security concerns, has declined to move the embassy and has signed a presidential waiver to keep it in Tel Aviv.

Who would be in favor of the move?

Israel would welcome a declaration from the United States saying Jerusalem belongs to Israel.

Palestine would have the most to lose if Trump recognizes Jerusalem as Israel's capital. In May 2017, the Palestinian group Hamas proposed the formation of a Palestinian state with Jerusalem as its capital.

The announcement would anger the rest of the Arab world as well. Saudi Arabia has called the idea a “flagrant provocation to Muslims.”

A senior Palestinian official said Wednesday that the decision means “the peace process is finished” because Washington “has already pre-empted the outcome,” The Associated Press reported.

On Tuesday, US personnel and their families were ordered to avoid visiting Jerusalem’s Old City or the West Bank. Palestinian factions have called for a “day of rage” over the announcement.

Here is the reaction from some world leaders to Trump’s expected announcement. (From the Associated Press)

Speaking to reporters in Moscow, President Vladimir Putin’s spokesman Dmitry Peskov said that the “the situation is not easy.” He said Putin discussed the issue with Palestinian President Mahmoud Abbas late on Tuesday and expressed his concern about “a possible deterioration.” Peskov said, however, that the Kremlin would refrain from commenting a decision that has not been announced yet.

British Foreign Secretary Boris Johnson is calling on the U.S. administration to present a Mideast peace plan because the decision clearly “makes it more important than ever that the long-awaited American proposals on the Middle East peace process are now brought forward.”

Iran’s Supreme Leader Ayatollah Ali Khamenei has condemned Trump’s imminent recognition of Jerusalem as the capital of Israel. The state TV’s website quotes Khamenei as saying that “when they (U.S.) claim that they want to declare Jerusalem as the capital of occupied Palestine, it shows their inability. ”

China has expressed concerns over “possible aggravation of regional tensions” in response to the expected U.S. announcement recognizing Jerusalem as Israel’s capital. Geng Shuang, a spokesman of the Chinese Foreign Ministry, said on Wednesday the China would monitor developments on the issue.

Syria’s Foreign Ministry says Trump’s expected announcement to recognize of Jerusalem as Israel’s capital is a “dangerous step” that will fuel global conflict. The ministry in Damascus issued a statement on Wednesday calling Trump’s imminent move the “culmination of the crime of the seizing of Palestine and the displacement of the Palestinian people.”

Two leading Lebanese newspapers have issued front page rebukes to Trump over his expected announcement recognizing Jerusalem as the capital of Israel. The An-Nahar compares the U.S. president to the late British Foreign Secretary Arthur Balfour, who a hundred years ago famously promised Palestine as a national home to the Jewish People, in what is known as the Balfour Declaration. The paper’s Wednesday headline reads: “Trump, Balfour of the century, gifts Jerusalem to Israel.”

Turkish Foreign Minister Mevlut Cavusoglu says the “whole world is against” Trump’s move to recognize Jerusalem as Israel’s capital and eventually move the U.S. Embassy there. He says that moving the embassy to Jerusalem would be a “grave mistake.”

Morocco’s King Mohammed VI, writing as head of the 57-member Organisation of Islamic Cooperation’s Al-Quds Committee, also expressed his “deep personal concern” and “the great concern felt by Arab and Muslim states and peoples” over the moves in a letter to Trump Tuesday. “The current step is likely to negatively impact the prospects of a just and comprehensive solution to the Palestinian-Israeli conflict,” the letter said.

Pope Francis is calling for the status quo of Jerusalem to be respected and for “wisdom and prudence” to prevail to avoid further conflict. “I pray to the Lord that its identity is preserved and strengthened for the benefit of the Holy Land, the Middle East and the whole world and that wisdom and prudence prevail to prevent new elements of tension from being added to a global context already convulsed by so many cruel conflicts.”